Process for continuous production of a large sized zinc-base alloy ingot

ABSTRACT

A process for continuous production of a large sized zinc-base alloy ingot which comprises: EMPLOYING AN ALLOYING FURNACE COMPRISING (I) A MIXING FURNACE HAVING AT LEAST ONE CHARGING WELL PROVIDED WITH A SIDE WALL OF SAID MIXING FURNACE AND AT LEAST ONE AGITATING MEANS EQUIPPED WITH A COVER WALL OF SAID MIXING FURNACE, (II) A MUFFLE FURNACE CONNECTED WITH SAID MIXING FURNACE AND HAVING AT LEAST ONE DISCHARGING WELL PROVIDED WITH A SIDE WALL OF SAID MUFFLE FURNACE AND (III) A PARTITION WALL HAVING AN OVERFLOWING CHANNEL AND INTERPOSED AT A BOTTOM OF A CONNECTED PORTION BETWEEN SAID BOTH FURNACES; INTRODUCING A CERTAIN AMOUNT OF A MOLTEN ZINC AND AT LEAST ONE ALLOYING METAL INGOT INTO SAID CHARGING WELL WHILE AGITATING SAID MOLTEN ZINC INTRODUCED; REPEATING THE INTRODUCTION OF SAID MOLTEN ZINC AND SAID ALLOYING METAL INGOT AT INTERVALS OF A FIXED TIME, THEREBY A MOLTEN ZINC-BASE ALLOY BEING CONTINUOUSLY FORMED AND INTERMITTENTLY OVERFLOWED BEYOND SAID PARTITION WALL FROM SAID MIXING FURNACE INTO SAID MUFFLE FURNACE; SUCCESSIVELY CASTING A CERTAIN AMOUNT OF THE RESULTING ALLOY INTO A LARGE-SIZED INGOT BY DIPPING UP SAID MOLTEN ALLOY FROM SAID DISCHARGING WELL AND INTRODUCING SAID MOLTEN ALLOY INTO A MOLD; AND REGULATING AN AMOUNT OF INTRODUCTION OF MOLTEN ZINC AND ALLOYING METAL INGOT PER UNIT TIME SO THAT THE INTRODUCING AMOUNT OF THE RAW MATERIAL INTO SAID MIXING FURNACE AND THE DISCHARGING AMOUNT OF THE MOLTEN ALLOY FROM SAID MUFFLE FURNACE MAY BE MAINTAINED IN A STATE OF APPROXIMATELY EQUILIBRIUM.

UntedState'SPatm 11191 .j tm 3,362,339 Shimizu 'gt l 4(451 'Jan.28 ,.l975

Mimet@ l 3, l 'N60 "LDNING C MEANS FoR Moto APPARATUS rrmste? mmHSTEP PATENTEUJMBIHTS i 3,862,839

' SHEET 4UB 0F v13.

CHARGED AMOUNT OFA MOLTEN ZINC (ton/hr) Om-bovOO-rTaM--S l l i 25 5D T INTRODUCED AMOUNT OF AJz-INOOT T kg/hr) sum 070i 13- FIG. 9

PAENrEnJmaalss Y vsnm, naar 13 PATENIEU .IAII 2 8 IBIS SHEET lOF I3 FIG. I3

STARTCP CASTING LIMIT SWITCH OF I MOLD @-ON ELECTRONIAGNETIC SWITCH @-CPP ISTOPPING MOLD- DRIVING APPARATUS) ELECTRCNIAGNETIC SWITCH @-DN IDESCENDING CARBON ELECTRGDE CP DETECTING APPARATUS BYII/IEANS OF CYLINDER) ELECTROMAGNET OF SAID ELECTRODE OFF l ELECTROMAGNETIC SWITCH I DESCENDING POURING PORT OF TROUGH BY MEANS OF CYLINDER @-ON B AT DESCENDING LIMIT, LIMIT SWITCH @-ON CASTING i CONTACT OF ELECTRODE AND MOLTEN ALLOY (ELECTROMAGNET ON) I ELECTRODE SEPARATED FROM ELECTROMAGNETIC SWITCH (OPERATING AIR-MOTOR OF DIPPING UP PUMP I VSURFACE OF MOLTEN ALLOY ELECTROMAGNETIC -ELECTRoMAGNI-:TIC ELECTROMAGNETIC SWITCH @Iy-DFP SWITCH @-CFF SWITCH @-DPP (RISING CYLINDER- ISTCPPING AIR-MOTORI (RISING CYLINDER- ARMADI- CARBON I I CP C VARII/IoI-'PDURING ELECTRoDI-:I DIPPING APPARATUS) PoRT) -`I l I t II l AT RISIIG I III/IIT C l I V I AT RIC SING.I III1IITr I IMIT WITCH I I I IMIT SWITCH SIGNAI. OFCCMPLETIDN I Y @TON OP CASTING @E 9N I ELECTRONIAGNETIC SWITCH @-ON (STARTING MOLD- DRIVING APPARATUS) I WATCHING NEXT CASTING PATENTEU JAN 2 8 |975 SHEET 11 of 13 FING. I4 IIT -PATENTEDJANZWS y 3,862,839

` sum leur 13 PROCESS FOR CONTINUOUS PRODUCTION OF A LARGE SIZED ZINC-BASE ALLOY INGOT BACKGROUND OF THE INVENTION i l. Field of the Invention The present invention relates to a process for continuously producing a large-sized zinc-base alloy ingot (normally` called tailored zinc ingot) which is charged and melted into a plating bath when a galvanized sheet is produced.

2. Description of the Prior Art Heretofore, large-sized tailored zinc ingots have been produced at the request of the users` the size or weight of which are in the range of from about 500 kg to about 1,000 kg of approximately rectangular parallelepiped shape. Such ingots, depending upon the request of the users, have a certain variation or a predetermined allowable range in the weight, but alloy component contents and ingot size are strictly specified. Also, in the production ofthe ingot, a large number of workers are required in each step, and at the tailored zinc melting furnace, zinc and desired alloying metal as the raw mateials are charged and melted to prepare a molten zinc base alloy having a predetermined composition, and the resulting molten alloy of a fixed amount is cast into a mold of a fixed size whose cross section is of almost concave rectangular parallelepiped type, and thereafter the ingot is pulled out from the mold, whereby the ingot is produced. With the recent increased production of galvanized sheet, however, the amount of demand for the mixed zinc ingot has also increased, and therefore in the production system where each step is dependent upon hand labor in the production system of the tailored zinc ingot as mentioned in the foregoing, this demand can no longer be satisfied. Accordingly, a need for development of a production system capable of mass production of the tailored zinc ingot has been strongly felt in this field of art.

BRIEF DESCRIPTION OF THE DRAWING FIG. l is a flow sheet showing one embodiment of the process according to the present invention.

FIG. 2 is a top view of one embodiment of the apparatus for use in the second step of the present invention.

FIG. 3 and FIG. 4, are, respectively, a side view and a front view of the apparatus shown in FIG. 2.

FIG. 5 is a horizontal cross-sectional view of one ernbodiment of the alloying furnace for use in the third step of the present invention.

FIG. 6 is a vertical sectional view of the alloying furnace in FIG. 5.

FIG. 7 is a vertical sectional view of the alloying furnace in FIG. 5.

FIG. 8 is cross section along the line B B in FIG. 5.

FIG. 9 is a vertical cross section of the agitating means suitable for use in the alloying furnace in FIG. 5.

FIG. l0 is a chart graph showing the relation of amount of mixing raw materials in case the zinc base alloy of one example to be melted by the present invention in various mixing amounts, and showing the relation between the amount of the charged molten zinc and required time for melting the aluminum ingot.

FIG. 1l is a side view showing one embodiment of the apparatus in the fourth step of the present invention.

FIG. 12 is a plan view of the apparatus in FIG. 1l.

FIG. 13 is a flow sheet showing one example of the operating mechanism system of the fourth step of the present invention.

FIG. 14 is a plan view showing one embodiment of the fifth step of the present invention.

FIG. l5 is a longitudinal cross section showing the cross section of the mold portion in FIG. I4.

FIG. 16 is a transverse cross section showing the cross section of the mold portion in FIG. 14.

FIGS. 17, 18, 19 and 20 are cross sections of the coupling for rolling over the mold.

SUMMARY OF THE INVENTION The purpose of the present invention isto provide a process for production of a large-sized tailored zinc ingot which is particularly suitable for the mass production system for satisfying the above-mentioned demands and also continuously and mechanically practicing the entire steps ranging from the preparation of the molten zinc base alloy after the melting treatment of the raw material to casting and withdrawing or pulling out of the ingot from the mold.

In accordance with the present invention, disadvantages ofthe conventional alloying furnace for theproduction of zinc base alloy as will be described hereinafter are avoided and an alloying furnace capable of continuously producing a zinc base alloy is provided.

The zinc base alloy ingot for use in the production of galvanized iron sheet is allowed to have a certain variation as to its composition in accordance with the demand of users, but considerably strict or severe composition specifications have been applied. Under the circumstances, for the production of the molten zinc base alloy in the conventional production of the zinc base alloy ingot, a batch system capable of making adjustment of the alloy composition has been employed. Namely, the whole part or almost the whole part of the molten metal in the alloying furnace which has been produced by the first charging of the raw materials to be mixed is used for making the ingot, and then the next raw materials are charged and mixed, and thereafter the materials are melted and such operation has been repeated. In thistype of the conventional production of molten zinc base alloy, the melting method of the one batch system has been employed, and therefore an alloying furnace of relatively large capacity is required and, moreover during the melting period of the zinc base alloy by the charging of raw materials, the casting operation of the ingot .has to be suspended, and also durin g` the casting operation, the melting operation of the zinc base alloy has to be suspended.

The present inventors have developed in the first place an alloying furnace for melting the zinc base alloy which is capable of continuously operating the alloying furnace without interruption of the ingot casting operation.

The present invention consists of employment of the abovementioned improved alloying furnace and also of adding one or more improved features to this alloying furnace.

Also, the purpose of the present invention is to provide a process for continuous production of a largesized zinc-base alloy ingot which comprises employing an alloying furnace comprising (i) a mixing furnace having at least one charging well provided with a side said both furnaces; introducing a certain amount of a molten zinc and at least one alloying metal ingot into said charging well while agitating said molten zinc introduced; repeating the introduction of said molten zinc and said alloying metal ingot at intervals of a fixed time, thereby a molten zinc-base alloy being continuously formed and intermittently overflowed beyond said partition wall from said mixing furnace into said muffle furnace; successively casting a certain amount of the resulting molten alloy into a large ingot by dipping up said molten alloy into a mold; and regulating an amount of introduction of molten zinc and alloying metal ingot per unit time so that the introducing amount of the raw material into said mixing furnace and the discharging amount of the molten alloy from said muffle furnace may be maintained in a state of approximately equilibrium.

Major steps to be preferably employed in the present invention are roughly divided as follows, and the alloying furnace is incorporated into the third step,

a. Step of producing raw material (molten zinc) first step b. Step of continuous dipping up and charging of fixed amount of molten zinc second step c. Step of continuous production of molten zinc base alloy .i third step d. Step of casting fixed amount of the resultant molten zinc base alloy automatically fourth step e. Step of automatic taking out of zinc base alloy ingot fifth step The present invention will now be described more in detail in the following, in accordance with the order of steps of the flow sheet (FIG. l) attached to this specification in which the above-mentioned major steps are divided into five steps and a schematic arrangement of apparatuses is illustrated.

lst Step: Step of producing raw material (molten zinc) In the present invention, it is designed so that even if a relatively small capacity molten zinc producing furnace (alloying furnace of FIG. l) is employed, the rate of operation of the furnace is raised, and also the molten zinc base alloy whose amount sufficiently meets the discharging amount of the melt comparable to that of a conventional furnace of large capacity is continuously produced. Therefore, the starting zinc metal which i's the basic main component of the zinc base alloy is used in the molten state. For this reason, the raw zinc material obtained ata zinc-refinery, for example, distillation zinc, electrolytic zinc, refluxed zinc, etc. is charged and melted in the electrolytic zincmelting furnace or distllation zinc-melting furnace as shown in FlG. l in the first place, and it is maintained in the molten state at an appropriate temperature range. Also, among these raw zinc materials, if the zinc obtained at the refinery is in a molten state, the molten metal holding furnace is used instead of using the melting furnace mentioned above, and the raw zinc material may be temporarily charged and retained in such holding furnace. The starting zinc materials have variable impurity components vdepending on the refining method, and therefore in the allowable component range, one or more kinds of such raw zinc materials may be preferably used after mixing thereof. FIG. I, illustrates the case where two kinds of raw zinc materials are employed. When only one kind of raw materials is used, of course, only the raw zinc material melting furnace is sufficient, and also, using three kinds thereof` three raw zinc materials melting furnaces can be employed. And as for these raw zinc material melting furnaces, any melting furnaces having the conventional structure can be used, but it is necessary for such furnaces to be provided with the well for dipping up the molten metal at the suitable side wall of the furnace.

2nd Step: Step of continuous dipping up and charging of fixed amount of molten zinc This second step is a step for dipping up the molten zinc of the raw material which is produced in the above-mentioned first step in a fixed amount and then it is charged into the third step of zinc base alloy producing furnace (alloying furnace). ln this step any apparatus capable of charging a fixed amount of molten zinc to the alloying furnace sequentially can be employed, but it is preferable to use the apparatus to be described in the following.

Namely, as the apparatus in this step, the well is provided for at least one raw zinc material melting furnace or the holding furnace as mentioned above, and a pump for maintaining the level of the surface of the molten zinc in the well constant is installed in the vicinity of the well in order to cause overflow of the molten zinc by pouring the molten zinc constantly into the well from the furnace, and it is preferable to employ an apparatus for dipping up in a fixed amount the molten zinc charged into the well from the raw zinc material melting furnace or the holding furnace and charging it from the well into the alloying furnace.

Next, a molten zinc fixed amount dipping up and charging apparatus suitable for the present invention is described in accordance with FIGS. 2, 3 and 4 appended hereto.

A machine frame 3 is assembled above the upper part ofa well 2 provided on the side wall of the raw zinc material melting furnace l, and a motor 4 and a reduction gear 5 are installed in said machine frame. This motor 4 (Bayer cyclo variable speed motor) is capable of changing speed in the range of from 6.1 to 24.4 r.p.m. and the speed of rotation of cam shaft 8 can be Vregulatedtothe range of from 2.2 to 8.8 r.p.m. by the combination of the gears 6 and 7.

A cam 9 is fitted and fixed to the cam shaft, and a suspending angle 11 is provided on a-suspending fixture l0 which is rotatable and being fitted into a channel of said cam 9. A rod l5 for effecting vertical movement of a dipper 12 is pivotally connected to this angle 11. A molten metal dipper l2 is connected to rod 1S. The dipper l2 is supported by a supporting fixture 13 at its one end, and a trough 14 for transfer of the molten metal is provided adjacent the wall of the well 2. The suspending angle ll is made to move vertically by the rotation of the cam 9, and the dipper l2 is made to move in a seesaw stroke by this motion with the supporting fixture 13 serving as the fulcrum. Accordingly, when the level of the molten zinc in the well 2 is always maintained constant, the molten zinc is dipped up by a fixed amount at a time, and as shown in FIG. 3 by the arrow, it is discharged to the trough 14. Also, the seesaw stroke of the dipper will become more preferable when the dipper is made to move vertically by the suspending angle l1 and when the rod l5 is pivotally supported by means of a supporting fixture 16 which is used as the fulcrum. It desirable to place a balance weight 17 on one end of the rod 15 connected to the dipper so as to make the movement easy, as shown in FIG. 3.

In the apparatus mentioned above, if the capacity of the molten metal dipper 12 is such that one dipping up is assumed to be 70 kg, within the variable range of speed of rotation of the cam shaft 8 as mentioned above, the amount of the molten metal dipped up per l hour can be regulated to be in the range of from 9,200 kg to 37,000 kg. Thus, for example, as described in the specification of official gazette of Japanese Pat. No. 6064/63 (applicant: Mitsui Mining and Smelting Co., Ltd.), if a pump of a molten metal feeding apparatus or a molten metal dipping up pump similar to that used in the fourth step to be mentioned hereinafter is employed, the molten metal continuously overflows the well 2 from the raw zinc material melting furnace 1 and returns to the melting furnace and the amount of molten metal dipped up by the dipper 12 for one operation can be regulated by making the level of the surface of the molten zinc 18 constant, and the rotational frequency of the cam shaft 8 is set to a predetermined value, whereby the amount of molten metal dipped up per unit time can be regulated. As the molten metal feeding apparatus for feeding molten zinc from the raw material zinc melting furnace 1 to the well 2, an apparatus having a considerably a large molten metal feeding capacity as compared with the dipping up amount per unit time becomes necessary, and with the employment of this apparatus, the molten zinc is fed to the well 2 and the molten zinc is made to overflow and return from the well to the furnace and thus the level of the molten zinc in the well 2 can be maintained constant.

The trough 14 for transferring the molten zinc is capable of continuously charging the dipped up molten zinc into the mixing furnace of the alloying furnace as shown in FIG. l. Also, there is an advantage that particularly, if variable speed motor is used as the motor 4, the dipping up amount of the molten zinc of the dipper 12 in a fixed time can be regulated by merely setting the speed to a fixed value.

The apparatus shown in the appended FIGS. 2 through 4, is the most suitable apparatus to be employed in the second step of the present invention, and its structure is summarized in the following. Namely, there is provided an apparatus for feed a fixed amount of molten zinc to the third step, which apparatus comprises (I) a molten metal feeding apparatus provided in conjunction a zinc melting furnace having at least one well, said feeding apparatus having a capacity sufficient to hold the level of the surface of moltenv zinc constant and capable of constantly feeding the molten zinc to the well from the melting furnace, (II) a machine frame assembled on the well, (III) a variable speed motor installed on the machine frame, (lV) a suspending angle that moves vertically by the rotation of the cam, said angle being fitted to the cam coupled to the shaft of the motor, (V) a trough for feeding the molten zinc provided in the vicinity of the well, and (VI) a dipper connected to the suspending angle, said dipper being supported in such a way that its one end is dipped in the well at the lower limit of the movement of the angle to dip up the molten zinc and its the other end descends at the upper limit of the movement of the angle so as to discharge the molten zinc to the trough for feeding the molten zinc. The dipper makes a seesaw oscillating movement of a predetermined frequency per unit time by the operation of the motor having a fixed speed of rotation.

3rd Step: Step of continuous production of zinc base alloy This third step is a step in which a fixed amount of at least one alloying metal for alloying with a fixed amount of molten zinc which has been charged from the well 2 is charged and melted to produce zinc base alloy having a desired composition, and the resulting molten alloy is supplied to the fourth step of casting a fixed amount of the molten alloy continuously.

In the third step of the present invention, as already described in the foregoing, an alloying furnace is employed in which a mixing furnace having at least one opening for introduction of the raw material or a recess for introduction of the raw material which is generally called the well, is connected to a muffle furnace which is heated by the combustion of air-gas (or liquid) fuel, and a partition wall is provided at said connecting portion.

At the upper portion of this partition, an overflowing channel, for example, a gap is formed in the space formed by the furnace cover wall or a communicating hole capable of flowing the molten metal at a suitable height of the partition is formed, or a recess is formed on the upper end portion of the partition, and when the molten zinc base alloy in the mixing furnace reaches the fixed level, the molten zinc base alloy overflows the partition and flows into the muffle furnace. Also in the mixingv furnace, it is preferable to provide at least one opening on the cover wall for insertion of the agitating rod which is inserted through the cover wall. for agitating the melt.

The alloying furnace to be employed in the third step of the present invention has the foregoing structure, and it can be easily constructed by connecting the mixing furnace of the foregoing structure to the conventional alloying furnace or building a chamber corresponding to a mixing furnace mentioned in the present invention as part of a conventional alloying furnace.

The third step of the present invention has a feature in which the molten zinc base alloy having a desired composition is produced in the mixing furnace by means of the partition in the alloying furnace, and this resulting molten zinc base alloy is transferred and flowed into the muffle furnace sequentially, and thus the ingot casting operation is not required to be interrupted orsuspendedat all. In other words, it is a feature of the present invention that the raw material charging and mixing and melting are repeated intermittently in the mixing furnace, whereby the increased volume of the molten zinc base alloy in the mixing furnace occurs, andan operation is carried out so that the molten zinc base alloy having a desired composition only is fed sequentially to the muffle furnace.

The third step of the present invention will be described more in detail in the following with reference to the appended drawings FIGS. 5-8.

In FIGS. -8, numeral 3l is a mixing furnace-and 32 is a muffle furnace. The molten zinc is charged into a well 33 by trough 14 at a selected rate, and a fixed amount of the alloying metal ingot, for example, aluminum ingot is charged into the well. The bottom of well 33 communicates with mixing furnace 3l.

As explained in the foregoing, the charging of the aluminum ingot can be carried out, as shown in FIG. 1, by using a suitable charger capable of charging the aluminum ingotat a desired time. Numeral 35 is an opening for insertion of an agitating rod or an agitation means, and the agitating rod or agitation means is inserted through the opening to agitate the molten zinc to accelerate the speedy melting of the alloying metal. Similarly, the well 33 is provided with a mounting position 34 of the agitating means, and at this position, the melting and alloying can be accelerated. Numeral 37 is a partition arid as shown` in FIG. 8, an overflowing channel 38 is formed on the center of the upper end of the partition 37 to accelerate the overflow of the molten zinc, and the portion of the molten zinc base alloy whose amount has been increased by the newly charged raw material only passes the overflowing channel 38 and flows into the muffle furnace 32. Numerals 39, 40, 41 are openings for heating burners, and thus the solidification of the molten zinc base alloy at the mixing of the molten zinc and the alloying metal by the direct heating of the combustion gas of the burners can be prevented, and also fluidity is improved.

The molten metal which has been alloyed with a desired composition and sequentially overflowed is introduced from the molten metal inlet 48 to the muffle furnace 32, and its temperature is retained at a temperature suitable for casting the zinc base alloy ingot by blowing the combustion gas from the openings 39, 40 and 41 along the muffle wall 49 in FIG. 6 and FIG. 7. And then the combustion gas is led to a discharge opening 36 through the mixing furnace 31 and is discharged in the upper direction. The molten zinc base alloy in the muffle furnace 32 enters from the molten metal discharge port 47 provided at the bottom of the furnace to a well 50 and a suitable amount of the molten zinc base alloy from the well 50 is cast into the molds for casting the ingot. Further, numerals 42, 43, 44, 45 and 46 are ports for removing slag in the furnace, and in the present invention, it is preferable to provide at least one port for removing the slag as mentioned above.

The furnace wall, partition wall and well in the alloying furnace mentioned above are constructed with refractory bricks capable of withstanding the molten metal, and a part of the entirety of the surface of the furnace wall portion may be reinforced preferably by a iron or steel shell. Also, in order to maintain a proper temperature range of the molten metal in the alloying furnace, it is desirable to regulate the temperature by adjusting the amount of combustion gas by providing measuring holes 51 and 52 for measuring the combustion exhaust gas tempeature and measuring holes 54 and 55 for measuring molten bath temperature.

A smoke stack for combustion exhaust gas is installed on the upper part of the exhaust gas opening 36 of the mixing furnace 31.

In the present invention, the agitation in the mixing furnace 31 and well 33 may be accomplished by using an iron or steel rod, but in order to avoid as much as possible the contamination of the molten zinc base alloy, it is preferable to use, for example, the agitation means as shown in the appended FIG. 9 which rotates and agitates the molten metal by the motor drive by inserting an agitating rod made of refractory substance, for example, silicon carbide rod attached with agitating vanes at its tip.

FIG. 9 is a vertical cross section of the agitation means, and it includes a coupling 64 is fitted to an end portion 63 of a supporting shaft of an impeller 6l having an agitating vane 62 at its lower end portion, and they are arranged to be rotated as a unit. The impleller 6l can be prepared by mixing a suitable binder into silicon carbide and sintering it at high temperature after forming it to a desired shape. Also, the impeller 6l can be prepared by sintering or melting and casting one or more kinds of substances such as other refractory substances, for example, zirconia, alumina, silica, and magnesia, and or it may be formed by a thermal resistance steel material. As a coupling 64 for use in connecting the impeller 6l and the rotating shaft 65, a flange coupling as shown in FIG. 9 is preferable.

In order to fit a water jacket 66 to the rotating shaft 65 rotatably, a roller bearing 67 and a radial bearing 68 are fitted into both end portions of the shaft. The roller bearing is retained at a fixed position by means of a washer 69 for a bearing and a nut 70 for the bearing, and both its end portions are sealed by oil seals 71 and 72. Also, the radial bearing 68, similar to the roller bearing 67, is retained at a fixed position by means of a washer 73 for the bearing and a nut 74 for bearing, and both its end portions are sealed by means of oil seals 75 and 76.

The water jacket 66 is employed for preventing the shaft 65 and these bearing mechanisms from being overheated by heat conduction and radiant heat from the molten metal, and also for effecting smooth rotational operation. This waterjacket 66 consists of cylindrical double side walls and having a space 77 through which water flows, and cooling water is introduced from a plug 78 of the outside wall, and it is discharged from a plug 79. By putting water jacket covers 80 and 81 over the openings at both ends of the water jacket, the rotating mechanism is protected. Also, at an upper end portion of the rotating shaft 65,'there is provided by V-belt pulley 82 for effecting rotation of the shaft. A metal fixture 84 for fixing the water jacket 66 to a suitable machine frame is provided on the jacket to prevent vibration of the shaft 65 and also to prevent the weight of the agitation means from being applied on the furnace cover fire resistance bricks 83.

Under the coupling 64 of the impeller 6l, a socket tube-like sealing vane 85 is fixed and the vane is fitted into a channel 87 of the sealing ring 86 fixed to the furnace cover fire resistance brick, and a low melting point metal, for example, lead, is filled in the channel. In this type of seal mechanism, the ring 86 is heated by the radiant heat from the molten metal, and the metal filled in the channel 87 is melted, entry of the atmospheric air at the time of operation of the agitation means is prevented and also the rotation of the impeller 6l is carried out smoothly.

In the third step of the present invention, the purpose of feeding zinc in the molten state into the well 33 is to effect complete mixing of the molten zinc base alloy,

which is uniform from the standpoint of composition, as mentioned above, in the well 33 and the mixing furnace 3l, and at the same time, to complete the melting of the alloying metal, for example, the aluminum ingot` Namely, in order to supply into the alloying furnace the molten zinc base alloy in an amount nearly equivalent to an amount of the molten zinc base alloy to be discharged or dipped up .for ingot casting from the alloying furnace, it is effective to supply the zinc which is the principal component of the casting ingot composition in the molten state. Also, in the third step of the present invention, in order to melt the alloying metal into the molten zinc in a predetermined limited time, the agitation for accelerating the alloying process is carried out in the mixing furnace by means of the agitation means mentioned in the foregoing.

FIG. 10 is a diagram showing with curve l the relation between the charging amount of raw material zinc and the charging amount of aluminun ingot in the case of producing a molten zinc base alloy having about 0.23 wt% of aluminum content in the mixing furnace, and also showing with curve 2 the relation between the required time for ideal melting (minutes) of the aluminum ingot in the charged zinc raw material as shown in the curve l and the charging amount of the zinc. When the molten zinc base alloy is discharged from the alloying furnace at a rate of about 6 tons per l hour, the aluminum ingot that is melted is 13.8 kg per one hour according to the curve 1, and the molten zinc base alloy thus formed has to be supplied to the alloying furnace. But supposing the aluminum ingot is charged as a 5 kg lump which is easily available on the market, the required time for ideal melting mentioned above means a value which is obtained for determining the time (minutes) required for melting the 5 kg aluminum ingot in relation to the supply rate of the molten zinc mentioned above. Accordingly, when the molten zinc base alloy is required to be produced at a rate of about 12 tons per l hou-r, it is necessary to charge one 5 kg aluminum ingot, about each l 1 minutes. In this case, about 2.2 tons of the molten zinc base alloy is produced about each ll minutes.

In case the molten zinc base alloy of a fixed composi tion of a desired amount in the limited time as set forth above is introduced to the muffle furnace, the temperature of the molten zinc at the time of adding the aluminum ingot greatly influences the required time for melting the ingot. An examination has been made as to how the amount melting of 5 kg of aluminum ingot changes in case the temperature of the molten zinc is varied, and the results shown in the following Table l were obtained.

The results of Table l are values obtained when three aluminum ingots weighing 5 kg per ingot were added to about 6.5 tons of moltenzinc, and the molten zinc was agitated by steel rod with hand working, and a molten zinc base alloy having about 0.23% of aluminum content was produced. It has been confirmed that results similar to the Table l were obtained for the melting condition of the aluminum ingot the weight of one ingot being about 2 kg, about 3 kg and about 4 kg, respectively.

In the third step of the present invention, although the temperature of the molten zinc varies according to the discharging amount of the molten zinc base alloy discharged from the alloying furnace per unit time in the fourth step to be mentioned hereinafter, it is preferable to hold the molten zinc charged from the second step into the well 33 of the mixing furnace 3l to at least about 500C, and with such temperature control, molten zinc base alloy can be produced at u rate of 30 to 50 tons per hour. And the molten zinc base alloy which has been produced in the mixing furnace 3l by the first charging of the raw materials can have a desired range of composition withfrespect to the zinc base alloy ingot, namely the specified component content range of said composition can be properly maintained because as only the molten zinc base alloy corresponding to the quantitatively increased amount caused by the second charging of the raw materials is introduced into'the muffle furnace 32 by means of passage 38. And also as described above, an operation of feeding molten zinc base alloy whose composition has been controlled is repeated intermittently. Therefore, it is possible to supply the molten alloy from the mixing furnace 3l into the muffle furnace 32 in amounts of the molten alloy per unit time corresponding to the amounts intermittently removed from the mufe furnace and by properly regulating the cycle time of such intermittent feeding operation. Accordingly, the molten zinc base alloy corresponding to the amount of molten zinc base alloy to be fed for normal casting in the fourthvstep of the process or more than such amount can be retained in the muffle furnace of the alloying furnace. The casting operation of the molten alloy and the melting operation of the raw materials can be almost continuously carried out without any interruption of the operation.

The third step of the present invention is explained using the aluminum ingot as the alloying metal in the foregoing, but it goes without saying that besides the aluminum ingot, any type of materials such as zinc base alloy containing aluminum, magnesium, copper, etc., or various kinds of alloying components which are demanded by users can be alloyed in molten zinc by treating them similar to theecase of the aluminum ingot.

Also, such alloying metal can be charged in fixedl amount into the mixing furnace by a mechanical means, and when the fixed amount of charging of the alloying metal is synchronized with the fixed amount of charging of the molten zinc whichk corresponds nearly to the amount of the molten zinc base alloy to be discharged from the alloying furnace, the third step can be carried out easily by a small number of workers. Furthermore, in the third step, the molten zinc base alloy can be produced nearly continuously, even if the amount of molten zinc base alloy to be consumed per unit time becomes considerably large, the alloying furnace itself can be made of relatively small capacity.

And in this third step, the use of the raw material ,zinc in the molten state is a necessary condition, and for this reason, it is necessary to employ the melting furnace for the zinc raw material or the molten metal holding furnace as described in the first step, but even when using the various kinds of raw zinc materials whose contents of lead, iron and/or cadmium, etc., are different, there is an advantage that the contents of the components contained in the molten zinc can be easily regulated by changing the mixing amounts of the raw zinc materials in the mixing furnace. Moreover. in the zinc refining factory, the raw zinc material can be obtained in the molten state, and in such a case, these raw zinc materials can be utilized in the present invention as is, and thus the heating expense for melting can be saved.

ln order to maintain a casting temperature of the molten zinc base alloy at a proper desired'temperature range, it is preferable to measure the temperature of the molten zinc base alloy in the muffle furnace 32 and to provide a temperature measuring hole in the vicinity of the well 50 in FIG. 5 for regulating the heating temperature and the casting temperature of the molten zinc base alloy.

4th Step: Step of automatic casting of fixed amount of molten zinc base alloy This fourth step is a step for sequentially casting a fixed amount of the molten zinc base alloy into a mold automatically which alloy having the desired composition has been produced and having a desired in the third step. And in this fourth step there is employed an apparatus for casting a fixed amount of the molten alloy, said casting apparatus being installed in conjunction with the well 50 of the alloying furnace of the third step.

The casting apparatus comprises a level detecting apparatus for detecting the level of the surface of the molten alloy at a fixed position when the molten alloy is cast into the mold and a dipping up apparatus for dipping up and casting a fixed amount ofthe molten alloy into the mold from the alloying furnace, and they are installed at the positions shown in FIG. l. Now, this casting apparatus starts to operate when the mold is stopped at the immediately preceding position of the casting apparatus, while the operation is arranged to take place on the basis of a command from the surface level detecting apparatus and that electromagnetic switches and limit switches are provided at each operating portion in the respective apparatuses, and each said operating portion is arranged to make a fixed time operation by the operating commands.

Next, the fourth-step is described more in detail on the basis of one embodiment of the casting apparatus as shown in the appended drawing.

FIG. 1l is a side view of the casting apparatus installed in association with the well 50 of the alloying furnace, and FIG. l2 is a plan view of the apparatus of FIG. 1l.

In these drawings, the surface level detecting appara tus 91 and the dipping up apparatus 92 are installed nearly in series. The mold 93 is set on the mold supporting fixture 96 movably supported by wheels 94 and 95. The mold is directly below the detecting apparatus 91 by means of angles 97 connected to the mold driving apparatus which is not shown in the drawing. At this time the mold is in nearly parallel with the well 50. The supporting shaft of this mold 93 is made eccentric and permits inversion of the mold, and it has been devised so that the ingot after the completion of the casting is easily removed by inverting the mold when it reaches a location spaced from the casting apparatus. As to this type of ingot inversion and removal, they will be described in the fifth step to be provided hereinafter. Also, it is preferable to make the supporting fixture 96 ofthe mold as a circular turn table, and a drive apparatus is installed in its center or its outer periphery. Several pieces of angles 97 are provided for carrying the molds, and the mold can be sequentially transported through an arc of 360 rotation. The stopping of the mold 93 at a fixed position, for example, can be made by transmitting the operating command of the limit switch to the mold driving apparatus. The limit switch is installed at a position for contacting the mold 93 and at a position close to the said fixed position. Simultaneous with the stopping of the mold driving apparatus, the casting apparatus starts its operation. Namely, a carbon electrode 98 of the detecting apparatus 91 is made to decend to a fixed position by means ofa cylinder 99 (compressed air cylinder) for lifting or lowering the carbon electrode. A pouring port 101 of a trough of dipping up apparatus 92 for dipping up the molten alloy from the well 50 is made to decend to a fixed position by means of acylinder 102 (oil pressure cylinder). At the lower limit of the position of the pouring port 101 of the trough 100 and the carbon electrode 98, a dipping up pump 103 for dipping up the molten alloy starts to operate. This dipping up pump 103 consists of an air motor 104, a compressed air feeding pipe 105 and a molten metal pumping pipe 106. The lower end portions of the compressed air feeding pipe 105 and the pumping pipe 106 are arranged to force the molten alloy at the end portion of the pumping pipe to the molten alloy discharge port 109 by the compressed air from the end portion of the feeding pipe 105 at the bottom portion of the well 50 of the alloying furnace. The molten alloy from the discharge port 109 is charged into the mold 93 by lowering the trough 100, and the surface of the charged molten alloy rises in the mold. when the surface of the molten alloy comes to contact with the carbon electrode 98 of the level detecting apparatus 91, both terminals of an electromagnet 110 disposed on the upper part of the electrode are shortcircuited and thus the electromagnet starts to operate.

A switch mechanism is constructed in such a way that the operation of the electromagnet 110 of the level detecting apparatus 92 is effected by connecting one terminal of the electromagnet with the electrode 98 and the other terminal to a suitable portion of the mold whereby the pow'er source is switched on by the contact of the surface of the molten alloy and the electrode. when this switch is turned on, the carbon electrode is attracted by means of the electromagnet and is separated from the surface of the molten metal.

As shown in FIG. 11, the electromagnet 110 and the carbon electrode 98 are iointly lifted above the mold 93 by the lifting of the arm of the cylinder 99 for lifting the electrode, Simultaneous with the operation of the electromagnet 110 mentioned above, the operation of the dipping up pump 103 stops and the arm of the cylinder 102 for lifting the pouring port 101 is lifted, and the molten alloy remaining in the trough 100 and the molten alloy fed to the said trough by the rotation of the air motor 104 for driving the pump 103 are respectively returned to the well 50. It is possible, however, to charge all of the remaining molten alloy in the trough into the mold by delaying the operation of the cylinder for lifting the trough 100 by means of a timer. Namely, the trough 100 is caused to make as oscillating or seesaw movement by the operation of the cylinder for lifting or lowering the pouring port by making the 

1. A PROCESS FOR CONTINUOUS PRODUCTION OF LARGE SIZED ZINCBASE ALLOY INGOTS, EMPLOYING AN ALLOYING FURNACE COMPRISING A MIXING FURNACE, AT LEAST ONE CHARGING WELL COMMUNICATING WITH SAID MIXING FURNACE THROUGH A WALL THEREOF, AT LEAST ONE AGITATING MEANS EXTENDING INTO SAID MIXING FURNACE, A MUFFLE FURNACE CONNECTED WITH SAID MIXING FURNACE, A MUFFLE FURCHARGING WELL COMMUNICATING WITH SAID MUFFLE FURNACE THROUGH A WALL THEREOF AND A PARTITION WALL HAVING AN OVERFLOW CHANNEL AND INTERPOSED BETWEEN SAID MIXING AND MUFFLE FURNACES; COMPRISING THE STEPS OF: INTRODUCING A SELECTED AMOUNT OF MOLTEN ZINC AND AT LEAST ONE ALLOYING METAL INGOT INTO SAID CHARGING WELL WHILE AGITATING SAID MOLTEN ZINC, AND SIMULTANEOUSLY MELTING SAID INGOT AND MIXING THE THUS-FORMED MOLTEN ALLOYING METAL WITH SAID MOLTEN ZINC TO FORM IN SAID MIXING FURNACE A MOLTEN ZINC-BASE ALLOY; REPEATING THE INTRODUCTION OF SAID MOLTEN ZINC AND SAID ALLOYING METAL INGOT INTO SAID CHARGING WELL AT FIXED TIME INTERVALS AND EFFECTING MELTING OF THE THUS-ADDED INGOTS AND MIXING THE RESULTING MOLTEN ALLOYING METAL WITH THE MOLTEN ZINC WHEREBY A MOLTEN ZINC-BASE ALLOY IS CONTINUOUSLY FORMED IN SAID MIXING FURNACE, AND INTERMITTENTLY OVERFLOWING SAID MOLTEN ZINC-BASE ALLOY FROM SAID MIXING FURNACE PAST SAID PARTITIONN WALL INTO SAID MUFFLE FURNACE; INTERMITTENTLY AND SUCCESSIVELY CASTING A SELECTED AMOUNT OF THE MOLTEN ZINC-BASE ALLOY FROM SAID MUFFLE FURNACE TO FORM A LARGE SIZED INGOT THEREOF BY FEEDING SAID MOLTEN ZINC-BASE ALLOY FROM SAID DISCHARGING WELL AND INTRODUCING SAID MOLTEN ZINC-BASE ALLOY INTO AT LEAST ONE INGOT MOLD; AND REGULATING THE AMOUNT OF MOLTEN ZIN ANDALLOYING METAL INGOT INTRODUCING INTO SAID CHARGING WELL PER UNIT TIME TO THAT THE AMOUNT THEREOF INTRODUCE INTO SAID MIXING FURNACE AND THE AMOUNT OF THE MOLTEN-ZINC-BASE ALLOY DISCHARGED FROM SAID MUFFLE FURNACE ARE MAINTAINED IN A STATE OF APPROXIMATE EQUALITY.
 2. A process according to claim 1, in which said discharging well is provided with a molten metal feeding apparatus comprising a molten metal pumping pipe extending into said discharging well and whose molten metal discharge port is located outside of said discharging well, a trough mounted for back and forth swinging movement and having one end adapted for receiving molten metal from the discharge port and having its other end forming a casting port adapted for casting the molten metal into an ingot mold, a first cylinder attached to said trough for raising and lowering the casting port toward and away from the ingot mold said ingot mold being provided with a level detecting apparatus comprising, an electrode adapted to be disposed above the mold, an electromagnet for raising and lowering the electrode, and a second cylinder provided at the upper end of the electromagnet for raising and lowering the electromagnet; in which the casting step comprises; positioning an ingot mold at a predetermined position and operating both cylinders, in response to the positioning of said ingot mold, to move both said trough and said electrode into their lower positions wherein said casting port is disposed directly above the mold and said electrode extends into the mold, and simultaneously operating said molten metal feeding apparatus and feeding molten metal into said trough and thereby into said mold until the molten metal in the mold contacts the tip of said electrode, then operating said electromagnet to move said electrode upwardly and operating said first cylinder to move said trough upwardly so that casting is discontinued.
 3. A process according to claim 1, employing a mold carrying apparatus for sequentially carrying and positioning ingot molds at fixed positions in the vicinity of said alloying furnace including a casting station and an ingot removal station, and said mold carrying apparatus is also provided at said ingot removal station with an ingot rolling over and taking-out apparatus, said ingot molds being made of metal and having a substantially concave mold cavity of rectilinear shape and adapted to have cast therein a fixed amount of the molten zinc-base alloy, said molds being pivotally mounted on coaxial eccentrically positioned shaft means so that their centers of gravity are offset from the respective pivot axes thereof, said ingot rolling-over and taking out apparatus having a fitting element detachably connectable to one end of said shaft means of the respective molds and capable of Effecting forward and backward motion to thereby engage and turn the shaft means and the mold as a integral unit in the direction in which the center of gravity shifts to a position on the opposite side of the pivot axis from the position it occupies during casting, an impact receiving post provided at a position where it collides with the upper end portion of the sidewall of the mold when the mold is rolled over through an arc of about 180* and an ingot receiving unit provided below the post; which comprises the additional steps of; intermittently moving said mold carrying apparatus to position a mold at the casting station, casting said molten zinc-base alloy into said molds when they are at the casting station adjacent said alloying furnace, solidifying the ingot castings and, said ingot removal station, rolling over the molds by engaging said fitting element with said shaft means and rotating said shaft means through an arc of about 180*, said mold colliding with said post and thereby automatically discharging from the molds the solidified ingots therein into said ingot receiving unit.
 4. A process according to claim 1, whrein said agitating means installed into said mixing furnace is an apparatus comprising a heat-resistant anti-corrosion impeller mounted on a supporting shaft, a drive shaft for rotating the impeller and a coupling for coupling said drive shaft to the upper end portion of the supporting shaft of the impeller, a water jacket fitted rotatably to the drive shaft, a socket tube-like sealing member fitted and fixed to the supporting shaft of the impeller and located below the coupling, a stationary sealing ring having a channel which is situated below said sealing member said channel being filled with a low melting point metal, and a means for rotating said shaft, the additional step compising continuously rotating said impeller immersed in the molten zinc in the mixing furnace.
 5. A process according to claim 1, including the additional step of cooling and solidifying the external surface of the molten cast ingot by spraying atomized water on the surface of the molten zinc-base alloy cast ingot in the mold said mold having sidewall and bottomwall surfaces, and then immediately pouring water on the entire surface thereof, and simultaneously cooling the sidewall and bottomwall surfaces of the mold with liquid or atomized water.
 6. A process according to claim 1, in which said charging well and said mixing furnace are connected in gravity, free-flow relationship so that the vertical levels of the liquids therein are the same, and said discharging well and said muffle furnace are connected in gravity, free-flow relationship so that the vertical levels of the liquids therein are the same, and the lower end of the overflow channel in said partition wall is located to permit passage of molten zinc-base alloy from said mixing furnace into said muffle furnace when the level of molten zinc-base alloy in said mixing furnace is above said lower end, including the steps of effecting flow of said molten zinc-base alloy from said mixing furnace into said muffle furnace when molten zinc and alloying metal ingot is added to said charging well.
 7. A process according to claim 6, including the step of continuously flowing hot gaseous products of combustion within said alloying furnace over said muffle furnace and into said mixing furnace to heat the contents thereof.
 8. A process according to claim 1, wherein said molten zinc is introduced into said charging well by providing at least one melting furnace having an overflow well at its sidewall for holding molten zinc; and at fixed time intervals, removing a selected amount of the molten zinc from said overflow well and introducing said selected amount of molten zinc into said charging well.
 9. A process according to claim 8, wherein said introduction of said molten zinc from said melting furnace into said charging well is carried out by the steps of (1) maintaining the level of the Upper surface of said molten zinc in said overflow well approximately constant by supplying molten zinc from said melting furnace to said overflow well in an amount sufficient to overflow the overflow well, and (2) effecting a regular back and forth swinging movement of a dipper in such a manner that at one end of its movement one end of the dipper is dipped to a predetermined depth into the molten zinc in the overflow well to dip up therein a fixed amount of the molten zinc, and at the other end of the movement of the dipper the thus dipped-up molten zinc in the dipper is discharged from the other end of the dipper into a trough provided adjacent said overflow well and leading into said charging well.
 10. A process according to claim 8, employing a molten metal feeding apparatus provided adjacent the overflow well and which feeds the molten zinc continuously from said melting furnace to the overflow well and which has a capacity sufficient to maintain the level of the upper surface of the molten zinc in the overflow well constant, and a feeding apparatus for feeding a fixed amount of molten zinc comprising a trough for transferring the molten zinc provided adjacent the overflow well, a variable speed motor, a vertically movable connecting rod fitted to a cam coupled to said motor, said rod being moved vertically by the rotation of the cam, a dipper connected to said rod and mounted for back and forth swinging movement disposed so that one end of said dipper extends a selected distance into the overflow well when said connecting rod is in its lowermost position to receive a selected quantity of molten zinc therein and the other end of said dipper descends as the connecting rod is raised to its uppermost position to discharge the molten zinc in the dipper into the trough, including the step of effecting back and forth swinging movement of the dipper at a fixed frequency per unit time so as to transfer molten metal from said overflow well to said trough via said dipper. 